Download Subcenters in the Los Angeles region

Subcenters in the Los Angeles region
Genevieve Giuliano
& Kenneth Small
Presented by Kemeng Li
Introductions and Objectives
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Metropolitan areas are now characterized by decentralized
patterns of employment rather than by monocentric urban
structure.
Subcenters are generated when the congestion effects are
high and agglomerative forces are strong.
This paper presents an empirical analysis of employment
and population patterns of subcenters in the Los Angeles
region.
The three objectives of this paper are
1.
2.
3.
To develop a method for systematically identifying employment
subcenters
To Apply the method to the data from Los Angeles region
To analyze the functions and distribution of centers
Data and Study Area
• The study region covers the urban
portions of Los Angeles, Orange,
Ventura, Riverside and San
Bernardino Counties, an area with
3,536 square miles land, 10.7
million people and 4.65 million
jobs.
• The area was divided into 1146
‘transportation analysis zones’
defined by Southern California
Association of Governments.
• The 1980 Census data provide
information on population
characteristics, employment, and
travel flows at spatial detail.
Definition and identification of
subcenters
• Among various ways to define subcenters, this paper agree
with McDonald(1987)’s that employment, not population is
the key to understanding the formation of urban centers; and
that a center is best identified by finding a zone for which
gross employment density exceeds that of its neighbors.
• A center is therefore defined as a continuous set of zones, each
with employment density above some cutoff D, that together
have at least E total employment and for which all the
immediately adjacent zones outside the subcenter have density
below D
• Density cut-off D is chosen to be 10 employees per acre,
minimum total employee E is chosen to be 10,000
Identification of subcenters and
their characteristics
• Using these criteria, this
paper identify 32 centers
(listed in table1)
• The four largest centers
form an arc from Santa
Monica through
downtown Los Angeles,
which we call the Wilshire
Corridor. These four plus
one smaller subcenter
(No22) would form one
giant center, 19 miles long.
We call these five centers
together the core.
Locations of Employment Centers
Findings about subcenters
• Dominance of the core centers ----The five centers in
the core contain more tan half of all jobs located in
centers. The core’s average density, 29 employee/acre
is higher than most other centers. Downtown Los
Angeles, with just over one-half percent of the
region’s land area, contains 10 percent of jobs within
the region and 31 percent of all job within centers.
• The region’s overall employment pattern is a dense
center surrounded by areas of gradually declining
density. Center’s distance from the highest density
zone of downtown LA is strongly correlated with
employment density.
Findings about subcenters
• Table 3 shows the distributions of total employment
& employment density across samples of centers. We
can see that the largest, densest centers tend to be
close to the core.
• Centers have a high concentration of population,
accounting for 9 percent of the region’s total. (While
the centers’ area accouts 3% of the region’s total).
Employment-population ratio are surprisingly low,
even in the main center. The average employmentpopulation ratio for all centers is 1.55, less than four
times the average for the entire region.
The functions of employment centers
• We want to examine the whether the agglomeration economies
generating subcenters apply only within an industry (creating a
tendency for some centers to specialize) or apply to an entire
complex of industries (creating centers with mixed activities)
• Cluster Analysis --First, the paper classified eight industrial sectors to examine
this question. Manufacturing, transportation, communication,
utilities, and whole sale trade together form a group of
production-oriented sectors accounting for an employment
share of 41 percent, the other three sectors, all service oriented ,
account for 55 percent.
Cluster Analysis ---The functions of
employment centers
• Cluster analysis is to use the 32 centers as observations and
use the eight industry shares as variables. Each observation is
described in terms of all the eight variables (represented by a
point in a eight dimensional space). The ‘Distance’ between
two centers in the eight dimensional space reflects the
dissimilarity of the two centers in terms of their function.
• Observations that are measured to be close to each other in the
eight dimension space form a cluster.
• The analysis suggest that five clusters best describe the
subcenters. Shown in table 5.
Cluster Analysis Result
Cluster analysis---The functions of
employment centers
• Overall, the cluster analysis suggests that subcenters play
diverse roles within the regional economy. Downtowns
continue to function as administrative, service, and retail
centers with substantial amounts of other industry. The
specialization of centers in services, manufacturing may be
indicative of spatial differentiation that occurs as regions
become heavily urbanized.
• The more service-oriented centers tend to be closer to the core
area. The result suggest that congestion effects (including land
costs) may repel production-oriented activities as the level of
concentration increases.
• At the same time, the four large centers in the core are in four
different clusters, suggesting further that even at this level the
urban system requires a variety of types of centers.
Conclusion
• This paper identified 32 employment
subcenters in Los Angeles region using a
consistent method.
• We find the economic activity is heavily
concentrated along a linear core area
consisting 5 centers.
• The cluster analysis suggests that the
employment in subcenters occurs in
recognizable industry-mix patterns ranging
from highly specialized to diversified.